a(n) = 8^n + 7^n - 1^n.

Terms

a(0) =1a(1) =14a(2) =112a(3) =854a(4) =6496a(5) =49574a(6) =379792a(7) =2920694a(8) =22542016a(9) =174571334a(10) =1356217072a(11) =10567261334a(12) =82560763936a(13) =646644824294